Computer has a delay on powering up after pressing power button

Sorry for not replying sooner, crazy week.

If i press the power button directly on the MB (Which is orange and has power itself) nothing happens, no error code displayed either.

I saw that thread Phillip, does not appear to be the same thing. His is a constant 5 second delay and fan spin up delay. My issue is an inconsistent delay, cant find a pattern to it.

Tonight, it would not power on at all, left it for about 10 minutes, no change, tried a few more times, nothing. Took the cover off, pressed the power button on MB a few times, nothing. Checked all cables seemed okay. So nothing changed, pressed the power button again for the hell of it and instant normal boot to windows.

No I don't have a spare one around, would need to do a RMA. Its possible but i find it quite odd, the PSU is only about 10-11 months old, no previous issues, not really stressing it.

So an update on this, I started having massive powering on issues again. I replaced the case and still had issues.

For the last week in order to get the PC to boot I have had to turn off PSU, pull power cable, let it sit for about 5 minutes, plug in power and then it will turn on fine (No issues/errors after power on). Last night it would not boot at all. Pressing the power button did nothing, no fan spin ups or any indication of boot, (Tried above steps a few times with no luck)

I took out the PSU and Mobo, placed mobo on a cardboard box, breadboarding mobo (CPU / 1 stick of ram), hooked up CPU power (Tried both 4pin and 8pin) and Mobo power (24pin) and attempted to start it with shorting the power switch pins with a screw driver. No luck, no fan spin or anything. Mobo did have power though as power indication LED was on. (I also tried with different CPU power cable and CPU PSU sockets as the PSU comes with 2 cables and two 8 pin sockets for CPU power)

Now I found an old spare Mobo and spare 500w PSU, I tested the old PSU and Mobo (Breadboarded ) together, used screw driver to boot and the Mobo turns on, fans spin up.

Attempted old Mobo with new PSU (850W CM), power LED comes on but no boot, no fan spins.

Attempted new Mobo with old PSU (500W OCZ), power LED comes on, short pins and we have boot, fans spinning, error code display on Mobo going through its various codes.

Ran through the tests a few more times, each time the old PSU (500W OCZ) would power on the mobo, the new PSU (850 CM) would not. This told me I had a dead / faulty PSU (850W CM).

Now comes the interesting part. I take it back to the store today for RMA, they hook it up to this little test board they have (Like breadboarded Mobo but more compact and designed for testing, has CPU, Mobo, PCIe power connectors with a little CPU/FAN) - this tester powers on just fine, the guy is trying to tell me it is not the PSU and it is my Mobo, the PSU either works or does not. Fine I will check again.

Get into work and test the PSU on 2 different machines we have lying around, one machine (1) it will spin up the fans for a few seconds then turn off, never boots. Power LED on mobo is on.

Try it on second machine (2) and the first time I try, it boots fine, fans spin up and stay on for 2+ minutes before we turn it off. Attempt to turn it on again, no dice. Try a few more times with the different CPU cables, no luck.

So out of the 15 attempts or so, only once did the PC actually boot up on (2), on (1), fans would spin then nothing.

How can I prove to the shop guys this is a PSU issue when it worked fine on there tester but not on 4 different breadboarded mobos, where mobos worked with other PSU's and where I had only 1 successful boot out of about 40 total attempts.

What would cause this type of behavior on a PSU? Could I still have an issue on the Mobo?

Yeah, I am going to go down that route, it has a 5 year warranty on it.

Funny enough I tried it again last night on old Mobo, same setup as night before where it refused to power on anything, this time it boots no problem, retested about 5 times without issues. So I put it back into the case, hooked it all up and PC booted just fine.

Decided to leave it on until I can get time to go back to the store. It has been extremely frustrating having a PSU that only works when the gremlins feel like working. I am not sure if it has some kind of defective safety feature, like its picking up static charge or something which might cause this?

Anyway, appreciate your help and reply, thank you!